The successful resolution of many health issues depends upon diagnostic measurements. As the quantity of diagnostic tests increases, the drive for lower cost and reagent consumption will fuel a trend toward highly parallel, miniaturized instrumentation. This is best seen in electrophoretic separations, where nearly one hundred, simultaneous DNA restriction fragment analyses have been performed using multiple channels etched onto a single quartz chip. The goal of this project is to improve the performance of current, chip-based diagnostics by integrating detection optics onto the same chip as the electrophoresis instrumentation. Unfortunately, the millimeter dimensions of standard, integrated optical components are incompatible with the extremely close spacing of etched electrophoretic channels. To circumvent this difficulty, an alternative approach to integrated optics will be developed which uses reflective waveguides, bends and beam splitters. Reflective waveguides represent a new paradigm in integrated optics as applied to chip- based instrumentation. Because they do not work on the principle of total internal reflection, it is possible to design and construct bends and splitters of micron dimensions. In initial studies, a master chip made from silicon will be used to create inexpensive plastic replicas. The design of each optical component will be optimized with respect to maximizing throughput and minimizing losses. The overall performance of the chip design will be determined by separating biological mixtures of diagnostic importance. Later studies will be performed on a more expensive silica-on-silicon chip. The advantage of this material is the ability to create sources and detectors directly in the silicon layer.